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Chapter 14

Biology 1000 Chapter 14 York University.docx

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BIOL 1000
Angelo Belcastro

CHAPTER 14: CONTROL OF GENE EXPRESSION Regulation of Transcription Initiation  Promoters contain TATA boxes  RNA polymerase II cannot recognize promoter sequence, so transcription factors bind to TATA box and recruit Polymerase  Promoter Proximal region: located upstream from teh the promoter, where tancsription factors bind to o May have inhibitory or enhancing effects Activation of Transcription  Is initiated when general transcription factors bind to the promoter in TATA box  Recruits RNA polymerase  Activator binding to enhancer greatly increases transcription Repression of Transcription  Reduce rate of transcription  Bind to site of activators  Or have their own site, that somehow prevents interaction with coactivators Combinatorial Gene Regulation  Combining few regulatory proteins in particular ways, transcription of a wide array of genes can be controlled Coordinated Regulation of Transcription of Genes  Genes with related functions clustered and transcribed from one promoter onto a single mRNA  Steroid hormone regulation DNA Methylation  DNA methylation adds enzymes to cytosine bases in DNA (located in promoter region)  Transcription of genes controlled by those is reduced  An inherited methylated gene is not expressed  Epigenetics: change in gene is achieved w/o change in DNA sequence of gene  Enzyme remove methylated region from promoter, which activates gene Chromatin Structure  Genes located in regions where DNA is tightly wound around histone, are less active  Chromatin Remodelling: Process of changing chromatin structure o 1. Activator binds to a regulatory sequence upstream from the genes promoter and recruits nucelosome remodelling complex. Complex uses energy from the hydrolysis of ATP to slide along DNA to expose promoter, or restructure o 2. Activator binds to regulatory sequence upstream from genes promoter, and recruits an enzyme the adds acetyl groups to amino acids in the tail of histones in the nucelosome, where promoter is located. Acetylation removes positively charged amino acid, lysine, making histone less attracted to DNA. Loosens the structure, where the promoter becomes more accessible  Post-transcriptional Regulation  Cytoplasm  Translational Regulation  Protein Synthesis  Post-translational Regulation  after protein synthesis   Post-transcriptional Regulation Controls mRNA Availability  Directs regulation by controlling the availability of mRNA to ribosomes  Variations in pre-mRNA processing 
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